Well, it definitely will be nerfed if he sells it. As it stands I still think it is still in for a nerf: you know, maybe having the Wolfpack Rounds only dealing half the damage they do or something, but in any case, once everybody has a gjallarhorn: a) like I said, the game will be broken b) some people who didn't get the Gjallarhorn will be mad and quit c) a lot of new players will be discouraged when everyone has the best weapon that they can't (easily) get d) Gjallarhorn won't even feel rewarding anymore, for anyone. ...etc, it will just go downhill. So yeah, until it gets patched, Xur shouldn't stock it. Because if he does, you'll see teams of level 28's and 29's killing atheon within 1-2 time's vengeance.